public RowMergingIterator merge(List<Iterator<Row>> iterators) {
for (Iterator<Row> rowIterator : iterators) {
if (rowIterator.hasNext()) {
queue.add(peekingIterator(rowIterator));
}
}
leastExhausted = false;
return this;
}
@Override
public Row peek() {
if (!hasPeeked) {
peekedElement = new RowN(iterator.next().materialize());
hasPeeked = true;
}
return peekedElement;
}
public RowMergingIterator(
Iterable<? extends Iterator<? extends Row>> iterators,
final Comparator<? super Row> itemComparator) {
Comparator<PeekingRowIterator> heapComparator =
new Comparator<PeekingRowIterator>() {
@Override
public int compare(PeekingRowIterator o1, PeekingRowIterator o2) {
return itemComparator.compare(o1.peek(), o2.peek());
}
};
queue = new PriorityQueue<>(2, heapComparator);
for (Iterator<? extends Row> iterator : iterators) {
if (iterator.hasNext()) {
queue.add(peekingIterator(iterator));
}
}
}
@Override
public Row next() {
if (!hasPeeked) {
return iterator.next();
}
Row result = peekedElement;
hasPeeked = false;
peekedElement = null;
return result;
}
@Override
public void remove() {
checkState(!hasPeeked, "Can't remove after you've peeked at next");
iterator.remove();
}
@Override
public boolean hasNext() {
return hasPeeked || iterator.hasNext();
}